Apparatus for augmenting jet thrust



Feb. 28, 1967 s. DORNIER 3,306,525

* APPARATUS FOR AUGMENTING JET THRUST Filed NOV. 2, 1964 United StatesPatent Ofilice 3,306,525 Patented Feb. 28, 1967 3,306,525 APPARATUS FQRAUGMENTING JET THRUST Silvius Dornier, Friedrichshafen, Germany,assignor to Dornier-Werke, G.m.b.i l., Friedrichshafen (Bodensee),Germany, a corporation of limited liability of Germany Filed Nov. 2,1964, Ser. No. 408,008 3 Claims. (Cl. 230-95) In copending applicationSerial No. 407,638, filed October 30, 1964, now abandoned, there isdescribed an apparatus for augmenting jet thrust which is susceptible toa spatially more favorable installation than are the known mixing tubeswith their considerable longitudinal dimensions. The invention of thecopending application, supra, employs a substantially cylindrical ordrum-shaped mixing container having an inlet for a primary jetpositioned tangentially to the drum and having an opening in the centerof one wall for the inflow of the mixing medium, i.e., air. In thisconstruction, the secondary jet is discharged in an annular form fromthe periphery of the Wall opposite to that in which the opening for themixing medium is provided.

In the invention of the copending application, supra, mixing is effectedin a rotary motion instead of jet intermixture in a straight-line flowwhich was heretofore effected using jet pumps or other jet devices forthrust augmentation. In the construction of the apparatus of thecopending application, supra, the secondary jet is discharged from oneend of the container or drum in the form of an annular jet. In thisarrangement, a system of vanes is required at the level of the annularjet in order to obtain the desired effect. This requires, in addition toan increased manufacturing cost, additional weight and additionalover-all height. A further problem is presented by the thrust-reducinglow pressure area within the discharging annular jet.

It has been found that in the construction of the copending application,supra, a low-pressure area or zone is formed within the annularsecondary jet which does not permit the full development of the desiredthrust augmentation. The present invention provides a constructionwhereby this low pressure area within the annular secondary jet and theadverse effects thereof are eliminated. The present invention does notutilize any displaceable elements, which are customary in knownconstructions, because of the unfavorable increase in the over-allstructural height resulting therefrom and because of the additional flowresistance when using a mixing drum for thrust augmentation. In theconstruction of the present invention, a flow channel extending axiallythrough the drum and connecting the low pressure area within thedischarging secondary jet with the area of normal pressure at theopposite side of the drum is employed. The low pressure area thus canautomatically draw in additional air from the opposite side of the drum,which results in the elimination of the low pressure area. A variationof the present invention includes a housing mounted below thedischarging secondary annular jet and having a side opening there in. Inthis construction, the area enclosed 'by the discharging annularsecondary jet is traversed by the deflected secondary jet so that theadverse effects resulting from the thrust-diminishing low pressure areaare effectively obviated.

The invention will be further illustrated by reference to theaccompanying drawings in which:

FIGURE 1 is a sectional view through a mixing drum including anozzle-shaped connecting channel between the upper and lower endsthereof,

FIGURE 2a is a sectional view through a mixing drum having a deflectorhousing thereon and a side outlet opening, and

FIGURE 2b is a plan view of the apparatus of FIG- URE 2a.

Referring to the drawings, in FIGURE 1, reference numeral 1 indicates amixing drum housing, numeral 2 designates the inlet opening of a primaryjet entering the drum in a direction normal to the image plane, andnumeral 3 designates the inlet opening for mixing air. The deflectorvanes 5 are positioned in the annular discharge aperture for thedischarging secondary jet 4. Reference numeral 6 designates a higherpressure area above the mixing drum while numeral 7 designates a lowpressure area in the center of the annular secondary jet. Referencenumeral 8 designates the nozzle-shaped connecting channel between thehigher pressure area 6 above the mixing drum and the low pressure area 7therebeloW.

During the operation of the mixing drum, the low pressure area 7disappears as a result of the air 9 flowing thereinto from the higherpressure area 6.

In a particularly advantageous construction, the largest cross-sectionalarea Q of the connecting channel 8 corresponds to the cross-sectionalarea of the bottom of the housing 1. In order to ensure that thediffusor angle of the connecting channel 8 does not become excessivelylarge, which would result in cavitation, the mixing drum preferably hasa decreasing or tapered cross-section in the downward direction. It isalso advantageous if the entire bottom of the drum or housing isutilized as the dilfusor outlet opening.

In FIGURE 2a, the reference numeral 10 designates a deflector housingwhich is mounted on the end of the mixing drum 1 and has a side outletopening 11 preferably of an oval or rectangular cross-section. Duringoperation, the low pressure area which ordinarily is formed in theregion indicated by the numeral 12 can not build up because of thetransverse flow of the deflected secondary jet at that point. Thecross-sectional area of the deflector housing increases in the directionof the outlet opening 11 in order to accommodate the increased volume offlow in that direction.

The operation and construction of the mixing drum of FIGURE 2a isfurther illustrated in FIGURE 2b, which is a top plan view of theapparatus of FIGURE 2a.

The construction of the present invention may be employed in aparticularly advantageous manner in those cases where the mixing drum isnot employed directly as a thrust augmentor but as a flow source for'blow-ofi or exhaust lines which are to be operated at a low pressureand a high volume throughput.

It will be obvious to those skilled in the art that many modificationsmay be made within the scope of the present invention without departingfrom the spirit thereof, and the invention includes all suchmodifications.

What is claimed is:

1. An apparatus for converting a primary propellant jet of a low massflow and high flow velocity into a secondary propellent jet of highermass flow and lower flow velocity as a result of admixture of the jetwith a surrounding medium which comprises means for introducing theprimary jet tangentially into a generally cylindrical 3 mixing containerhaving an inlet opening in one of the end walls thereof for the inflowof the mixing medium, an annular outlet opening for the secondary jet inthe periphery of the other end wall, and a fiow channel extendingaxially through the container.

2. An apparatus according to claim 1 in which the How channel has anincreasing diameter as it approaches the end of the container having thesecondary jet opening therein.

3. An apparatus according to claim 1 in which the mixing container has adecreasing diameter as it approaches the end of the container having thesecondary jet opening therein.

References Cited by the Examiner UNITED STATES PATENTS 2,605,081 7/1952Alford 253-39 2,811,331 l0/l957 Wiegand 25339 2,938,658 5/1960 Foster230-95 3,041,010 6/1962 Foster 230-95 X FOREIGN PATENTS 522,974 4/1931Germany.

MARK NEWMAN, Primary Examiner.

D. HART, Assisrant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,306,525 February 28 1967 Silvius Dornier It is hereby certified that errorappears in the above numbered patent requiring correction and that thesaid Letters Patent should read as corrected below.

In the heading to the printed specification, between lines 6 and .7,lnsert Claims priority, application Germannseptj 26, 1964, D 45509Signed and sealed this 26th day of September 1967.

( A Attest:

ERNEST W. SWIDER Attesting Officer EDWARD-J. BRENNER Commissioner ofPatents

1. AN APPARATUS FOR CONVERTING A PRIMARY PROPELLANT JET OF A LOW MASSFLOW AND HIGH FLOW VELOCITY INTO A SECONDARY PROPELLENT JET OF HIGHERMASS FLOW AND LOWER FLOW VELOCITY AS A RESULT OF ADMIXTURE OF THE JETWITH A SURROUNDING MEDIUM WHICH COMPRISES MEANS FOR INTRODUCING THEPRIMARY JET TANGENTIALLY INTO A GENERALLY CYLINDRICAL MIXING CONTAINERHAVING AN INLET OPENING IN ONE OF THE END